I have been experimenting a bit with FASI in naphtha, which has not been considered a viable route. I have successfully precipitated dmt fumarate using FASI out of naphtha (FASI in Naphtha!), but questions remained about excess fumaric acid precipitating out of the solvent.

Endlessness recommended I conduct an experiment confirming that fumaric acid will not precipitate out of clean naphtha. In summary, fumaric acid will not precipitate so long as the naphtha is 'dosed' with 5% IPA by volume before the FASI is added.

FASI was prepared with 99% IPA (25g in a 473ml bottle), which was shaken and allowed to settle.

The FASI was added dropwise into two separate glass jars containing 30ml VM&P naphtha each.

Into the jar on the right was added 1.5ml IPA (5% by volume), and then the FASA was added dropwise into each jar.

The jar on the left (without previous addition of IPA) clouded when about 0.4ml of FASI was added.

The jar on the right did not cloud or precipitate, even after 6ml (20% by volume) of FASI was added.

The amount of FASI added is typically about 15% by volume, so the amount added is in excess of what would typically be required.

Conclusion: FASI in naphtha is likely possible without precipitating excess fumaric acid.

Thanks for doing this experiment and posting it

You're welcome--

I learned something new too. In my process, I thought the heating of naphtha is what allowed the fumaric acid to stay in solution. It turns out that isn't the case. Now I need to run a trial with dmt saturated solvent to see if fumarate will form at room temperature (I think it likely). If so, it makes this extraction process much easier.

I like working with naphtha much more than xylene or acetone, both of which are super stinky and less selective.

Couple of questions, Nitegazer.

After adding FASI to the saturated naphtha, how do you proceed with the precipitation of dmt-fumarate out of it? Do you freeze precipitate or fridge precip?

Were you able to reuse your naphtha after collecting the precipitate out of it? Did a water wash on it suffice to clean the FASI out of it?

Edit: I've noticed in one of your recent posts that you say naphtha should be heated to 50C for this experiment to work. Is that correct for the above post or was this employed at room temp?

Thank you for posting this update. I too have been looking for a way around this for some time. I've seen it being speculated in some posts here, in the past as well as in a more recent post involving the addition of acetone to naphtha(reply by Godsmacker to one of pastanostra's experiments) but never had the time to cope with this experiment or, more specific, with the eventual work that had to be put into recovering eventual partially-failed attempts.

I've taken the fumarate conversion route as a purification step often. I liked it more over backsalting in acidic water for a number of reasons. It took more time to go through all the steps but the result was always worth it.

I will definitely give this one a try as soon as i get the chance.

Thanks for the reply, Nereus-

I try to assist the precipitatation of fumarates by putting it in the fridge. That is done only because it seems to be a common practice-- and I don't think it hurts. I assume diffuse crystals come together more easily in a cool liquid. The point isn't to lower solubility, since fumarate isn't soluble in naphtha or ipa.

The heating of naphtha was really a red herring. I thought the heating was important to increase the solubility of IPA in naphtha, but I think I was wrong. I just started a cold precipitation (pre-dosed with IPA), which seems to be coming along fine. Once I have finished, and I confirm that excess fumaric acid isn't precipitating, I'll update my earlier threads on the topic.

Re-use of naphtha is the big question mark. The wiki states that xylene can be washed, and Endlessness has sugested that naphtha can too, but I haven't yet re-used naphtha to confirm the effectiveness of washing. The best test would be to distill the washed naphtha to measure the impurities, but that is beyond my skill and resources.

I may not run annother extraction for a while, so I don't know when I'll have the chance to test my washed naphtha. I don't know how much water to wash it with, but I'm hoping 1-2x the volume of solvent will be good enough.

I'm glad you're working on the same route-- too little has been posted on FASI/FASA. It doesn't require the evaporation of solvent, doesn't need freezing and is beautiful to watch happen. Please post your efforts -- I am hoping a solid tek could be put together in the future.